The present invention relates generally to maintenance vehicles having ground-engaging implements attached thereto and, more particularly, to belt drive systems adapted to deliver power to such implements from a vehicle prime mover.
Ground maintenance vehicles adapted to support and operate any one of a number of ground-engaging implements are known. For instance, riding tractors may support such implements as cutting decks, snow throwers, sweepers, etc. While some of these implements may be self-powered, e.g., tow-behind cutting decks having on-board engines, other implements typically receive take-off power from a drive shaft of the vehicle""s prime mover, e.g., engine. While the present invention is applicable to drive systems for use with most any ground maintenance vehicle and implement combination, it will, for the sake of brevity, be described with respect to commercial riding mowers having belly-mounted cutting decks.
For mowers having large engines, e.g., 20 horsepower (hp) or more, the engine may be mounted such that the engine drive or output shaft axis is oriented horizontally. The cutting deck, on the other hand, typically has a driven shaft having an axis that is oriented vertically. As a result, in order to deliver power to the cutting deck, rotary motion about the horizontal drive shaft must be converted to rotary motion about the vertical driven shaft.
Generally speaking, take-off power is provided to the cutting deck via either a belt drive system or a shaft drive system (or a combination of both). Shaft drive systems deliver rotational power through a driven shaft via appropriate gearing mechanisms and couplings.
While beneficial for many applications, shaft drive systems have drawbacks. For instance, shaft drive systems require numerous parts, e.g., bearings and gear boxes, as well as adequate structure to support the same. As a result, the cost and complexity is generally perceived to be higher than that for belt drive systems. Moreover, depending on the particular configuration, shaft drive systems may require increased maintenance, e.g., lubrication of bearings and gears, when compared to belt drive systems.
In typical belt drive systems found on riding lawn mowers, an endless belt extends between a vertical drive sheave attached to the horizontal drive shaft and a horizontal driven sheave attached to the vertical driven shaft. Belt drive systems in which the drive shaft axis and the driven shaft axis are not parallel and may even be perpendicular or approximately perpendicular to one another (or at least lie in separate planes that may be perpendicular or approximately perpendicular to one another) are often referred to in the art as mule drive systems. An example of a mule drive system for use with a riding tractor is found in U.S. Pat. No. 4,325,210 (Marto). To accommodate belt interconnection between the vertical drive sheave and the horizontal driven sheave, two idler sheaves are typically provided. The idler sheaves may generally be mounted in vertical planes for rotation about a transverse, horizontal axis.
While mule drive systems avoid some of the disadvantages of shaft drive systems, problems remain. For example, the horsepower carried by the belt is limited by its cross-sectional size, e.g., belts having larger cross-sections are able to transmit more power than those having smaller cross-sections. Although able to transmit correspondingly greater power, belts of larger cross-section have more limited rates of belt twist. As a result, as the size of the belt cross-section increases, the distance between the drive sheave and the idler pulleys must also generally increase.
To accommodate this increased spacing between the drive sheave and idler pulleys, either the drive sheave, e.g., the engine, may be raised or the idler pulleys may be lowered. Since the space available to lower the idler pulleys is limited, raising the engine is a more common solution. Raising the engine, however, results in an undesirably higher center of gravity for the mower.
Mule drive apparatus in accordance with the present invention overcome the above-identified problems and disadvantages by providing apparatus utilizing multiple mule drives, e.g., a first and a second drive belt each routed between a drive sheave and a driven sheave. As a result, belts having a smaller cross-section may be used without sacrificing total power transmission capacity, i.e., power transmission may be split between the two or more belts. In addition, apparatus of the present invention locate the idler pulleys at a more outboard location relative to the drive sheave. Therefore, the engine may be lowered while maintaining the desired distance between the drive sheave and the idler pulleys. By maintaining a lowered engine position, vehicles utilizing dual mule drive apparatus in accordance with the present invention are able to provide a vehicle having a lower center of gravity as compared to vehicles using conventional mule drive systems.
In one exemplary embodiment, a mule drive apparatus for delivering power to a cutting deck attached to a lawn mowing vehicle is provided, where the apparatus includes a powered drive sheave operable to rotate about a drive sheave axis. A driven sheave coupled to the cutting deck is also included wherein the driven sheave is operable to rotate about a driven sheave axis. The mule drive apparatus also includes a first endless belt and a second endless belt, each of the first endless belt and the second endless belt operable to frictionally engage both the drive sheave and the driven sheave.
In another embodiment, a mule drive apparatus for delivering power to a cutting deck attached to a lawn mowing vehicle is provided. The apparatus includes a drive sheave operable to engage a power take-off shaft of the vehicle, where the drive sheave is operable to rotate about a drive sheave axis. Further included is a driven sheave adapted to couple to the cutting deck where the driven sheave is operable to rotate about a driven sheave axis. A first endless belt and a second endless belt are also included where each of the first endless belt and the second endless belt is operable to frictionally engage both the drive sheave and the driven sheave. Positionable along a tension side of the first endless belt is a first guide pulley while a second guide pulley is positionable along a tension side of the second endless belt. A first idler pulley is positionable along a slack side of the first endless belt and a second idler pulley is positionable along a slack side of the second endless belt.
In yet another embodiment, a lawn mowing vehicle is provided. A cutting deck is attached to the vehicle as is a prime mover operable to provide power to at least the cutting deck. The vehicle further includes: a mule drive apparatus for delivering power to the cutting deck where the mule drive apparatus includes a drive sheave engageable with a power take-off shaft of the prime mover, the drive sheave operable to rotate about a drive sheave axis; and a driven sheave coupled to the cutting deck, the driven sheave operable to rotate about a driven sheave axis. Also included with the mule drive apparatus is a first endless belt and a second endless belt, where each of the first endless belt and the second endless belt is operable to wrap around and frictionally engage both the drive sheave and the driven sheave.
In still yet another embodiment, a method for providing power to a cutting deck of a lawn mowing vehicle is provided. The method includes coupling a first endless belt around both a drive sheave of a power take-off shaft and a driven sheave of the cutting deck. A tension side of the first endless belt is placed in contact with a first guide pulley and a slack side of the first endless belt is placed in contact with a first idler pulley. The method also includes coupling a second endless belt around both the drive sheave of the power take-off shaft and the driven sheave of the cutting deck. A tension side of the second endless belt is placed in contact with a second guide pulley and a slack side of the second endless belt is placed in contact with a second idler pulley.
The above summary of the invention is not intended to describe each embodiment or every implementation of the present invention. Rather, a more complete understanding of the invention will become apparent and appreciated by reference to the following detailed description and claims in view of the accompanying drawings.